Nice thing is, you aren't the first to invent this wheel and learning from others who have done exactly what you want to do is the best way!!!!

Aren't there legal requirements to let the tenant know?

Those aren't great fits for long distance investors. 

I've recently added a clause to my lease and my lease renewal that has them provide a contact person that is authorized to remove things on their behalf in the case of death or incapacitation.

It requires tenant authorization by sending the tenant an email.

As @Patricia Steiner said, in my state, an "As-Is" contract allows the buyer to walk away for any or no reason during the inspection period, while the "Standard" contract allows for the seller to remedy certain items to "working condition" and does not necessarily allow the buyer to back out scot-free.If you aren't sure of your contract, consult your Attorney, Realtor, or title company for some direction. 

This seems quite limiting if you're trying to BRRRR a property in under 6 months since so much of the out of pocket expense are the rehab costs which you aren't able to refi out of.Is it really as black and white of a choice as 1) wait 6 months to pull out the full 75% LTV or 2) if under 6 months only pull out the original cash purchase amount?

We aren't correctly sized but it could work for you. 

Ideally this would mean that this single family house would need to be a large 3 floors plus basement with ample space for the aforementioned as well as units which aren't 'weird'. 

I'd want to ensure they aren't crossed up there, but it may be that the property is owned by the homeowner still.